How many pounds of coffee?

Question

How many pounds of coffee that is 40% java beans must be mixed with 80 pounds of coffee that is 30% java beans to make a coffee blend that is 32% java beans? 

Answer 1

let x = pounds of beans at 40%

 

then 80p • 0.3 + x • 0.4 = (80 + x) • 0.32

expanding, 24p + 0.4x = 25.6p +0.32x

combining, 0.08x = 1.6p

x = 20p

 

Proof: 80p x 0.6 + 20p x 0.4 = 100p x 0.32

24p + 8p = 32p